The Preparation of Oriented Single Crystal Spheres of Intermetallic Compounds Between the Rare Earth and Iron Group Metals

摘要

Using minor modifications of a process previously developed (see AD-611 430), single crystal spheres up to 2 mm in diameter of Nd2Co17 and Y2Co17 were prepared. Details of the experimental work are presented. Attempts to find a suitable automatic temperature control scheme for the process were unsuccessful. As a result, impurity 'banding' of the zone-melted ingots remained a problem throughout the program and caused a lack of reproducibility in crystal growth experimental results. The ceramic material 'Lucalox' was found to be at least as suitable as Morganite alumina for use as a crucible material with rare earth-iron or cobalt melts. Efforts to orient the single crystal spheres by an optical Laue technique were unsuccessful, primarily because of the inability to consistently produce well-formed etch features exhibiting recognizable symmetry on the crystals. Etchant techniques tried included chemical etchants, thermal etching in air, and cathodic sputtering. Recommendations for future improvements in the growth process used with these materials are given. (Author)